The present invention relates to expansion joint seals of the type used for sealing an expansion joint gap against the intrusion of dirt, water or the like. This type of expansion joint conventionally comprises an elongated resiliently deformable strip seal in combination with a pair of rigid edge members which are installed on opposite sides of the gap and formed with cavities opening towards the gap for purposes of supporting opposite lengthwise extending edges of the strip seal.
A problem encountered with many available expansion joint seals is that during use their mounting bead portions become dislodged from one or the other of the edge members over part or all of the length of the seal with the result that the seal no longer functions for its intended purpose. Much of the problem stems from the fact that commercially available edge members are extruded through dies, which experience a substantial degree of wear during the extrusion process. As by way of example, extruded edge members on the order of 20 feet in length, such as might be utilized in a bridge joint, experience a progressive reduction in the size of its cavity, such that a given internal dimension of the cavity may vary upwards of almost 1/4 inch between opposite ends of the edge member. Further, while relatively uniformly sized extruded joint seals may be fabricated, it is nonetheless not unusual to find intermittent variations in dimension of the strip seal. As a result of these manufacturing variations, it has been common practice to size the mounting bead portion of the strip seal to the mean expected size of the cavities with the result that at one end of each edge member the mounting bead portion is loosely retained and prone to dislodgement from its receiving cavity, whereas at the other end of the edge member it is a difficult and time consuming operation to force the mounting bead portion into such cavity.
Further, in expansion joints of the type under consideration, it is inconvenient or impossible to insert the mounting bead portions of strip seals lengthwise within their associated cavities. Thus, the mounting bead portions must be designed so as to allow their size to be reduced sufficiently to permit insertion into the cavity through its opening, which faces the gap. A most common technique, as shown by way of example in U.S. Pat. Nos. 3,994,609 and 4,067,660, involves making the mounting bead portion of a hollow, relatively thin walled construction so as to permit compression thereof incident to insertion within the cavity. Unfortunately, the typical hollow mounting bead construction is such as to allow tension forces applied to the web to subsequently compress the hollow mounting bead sufficiently to permit dislodgement thereof from the cavity. These patents seek to remedy this problem by providing an outer surface of the mounting bead portion with a radius of curvature in its unstressed state, which is less than the radius of curvature of the rear wall of the cavity, such that the tendency of the outer surface of the mounting bead to assume the radius of curvature of such rear wall, as an incident to insertion, biases upper and lower surfaces of such mounting bead to expand into locking engagement with opposed surfaces of the cavity. A problem encountered with this type of construction, particularly adjacent the end of an edge member at which its cavity is smallest in size, is the difficulty of effecting insertion of the mounting bead portion in view of the tendency of the upper and lower portions of the mounting bead portion to move apart incident to deformation of the outer surface of the mounting bead portion to conform with the curvature of the rear surface of the cavity.
An alternate approach is suggested by U.S. Pat. No. 3,888,599 wherein the mounting bead portion of the strip seal has its outward surface shaped to essentially correspond in configuration to the inner surface of the cavity and is provided with a large concavity on its inner surface facing towards the gap, which serves to divide the mounting bead portion centrally thereof into upper and lower parts bendable relative to one another. A drawback of this construction is that it appears to require that a workman have access to the interior of an expansion joint, i.e. below the level of the strip seal, for seal installation purposes, and this is either inconvenient or not possible in most expansion joint installations of the type wherein joint seals of this nature would be expected to be employed. Moreover, the size and positioning of the concavity is such as to "weaken" the mounting head portion and facilitate its dislodgement from within the cavity of the edge member upon the application of downwardly directed tension forces to the web portion of the strip seal.